Embryonic stem (ES) cells have advantages over adult stem cells because these cells exhibit long-term proliferation in vitro, potentially providing an unlimited supply of tissue for meeting human transplantation needs. ES cells also exhibit pluripotent capabilities, giving rise to all cell types derived from the three embryonic germ layers. For these reasons, embryonic stem cells provide an excellent in vitro system for studying embryogenesis and other differentiation cellular events including vasculogenesis, the formation of a vascular network. The goal of the proposed research project is to induce the differentiation of embryonic stem cells down an endothelial cell lineage in order to study the cellular events in vasculogenesis. The hypothesis of the proposed research is that the differentiation of embryonic stem cell-derived endothelial progenitor cells can be induced through the use of mechanical forces. The specific aims of this proposal are to first induce vasculogenesis differentiation of endothelial progenitor cells using shear stress and/or biochemical growth factors. The level of differentiation of the stem cells will be evaluated using typical assays of cell surface marker expression of the endothelial cells and the undifferentiated embryonic stem cells. A uniform population of mature ES-derived endothelial cells will isolated from the ensuing cell populations. These mature endothelial cells will then be assayed for functional capabilities including their ability to self assemble into tube-like formations in vitro and their ability to respond to a dynamic environment. This proposed study will develop methods leading to a more uniform differentiation of stem cells towards a properly functioning endothelial cell population. [unreadable] [unreadable]